Electric toy model trains typically include an electronic audio speaker system incorporated within the locomotive engine car of the train to provide simulated locomotive warning horn or whistle sounds. Typically, voltage power is supplied to the audio speaker system of the locomotive engine car via one of the rails of the train track.
Toy model trains typically include an electronic user control box electrically connected to one or more of the train track rails. The control box typically has one or more levers, dials, or buttons which are manually adjustable and manipulatable by the user. In this way, the control box enables the user to manually control the voltage levels supplied to the electronic systems and motor of the locomotive engine car to control the toy train's speed, direction, and sounds.
In the past, a problem would often arise when the user would decrease the voltage supplied to the locomotive engine car to slow it down or stop it. Such a decrease in voltage supplied to the engine car would then make it impossible to activate the audio speaker system in the engine car because the decreased supply voltage would be inadequate to drive the speaker system. To solve this problem, a voltage doubler circuit or other voltage multiplier circuit was incorporated within the audio system of the engine car to ensure that the audio system could be properly activated with appropriately high voltage levels, even when the locomotive engine car itself was slowed down or stopped.
However, providing a voltage doubler created other problems. In particular, when a user increased the voltage supplied to the locomotive engine car to move the engine car at high rates of speed along the train track, the voltage doubler would automatically step up the voltage supplied to the audio system. As a result of such an increase in voltage, the various electrical components incorporated within the audio system needed to have higher voltage capacities. Despite the relatively high cost of such high capacity components, they often overheated and occasionally catastrophically failed.